While this particular tigger of the real bug was caused by 659d95221e
(hopefully fix both the "get stuck waiting for 3d" bug and the null
worldmode bug.), the real bug was lurking in the code since the dawn of
time (from sw32's perspective). This fix is as per LordHavoc's suggestion
(heh, despite the years, he knows his code), but I spent the time hunting
down the trigger to understand just what was going on.
It turns out that (0,0,0) is too close to a wall (probably on, but the
slight default offset is too close) and the above commit changed the first
rendered frame to be before the player origin was set rather than after.
This fix feels correct to me because noclipping around with the sw32
renderer would probably hit the same bug with a bit of bad luck. Thus
ensure the index resulting from zi never exceeds 65535.
e167300a84